Isobutylene-based terpolymers including isoolefin, styrenic, and multiolefin derived units have been disclosed in U.S. Pat. No. 3,948,868, U.S. Pat. No. 4,779,657; and WO 01/21672. To be useful in, for example, a tire tread or tire sidewall as part of a multi-component automobile tire, the terpolymer must desirably be both sulfur curable, and compatible with other rubbers such as natural rubber and polybutadiene. Further, in order to serve as a tire tread, the terpolymer compositions must possess abrasion resistance as well as traction. These properties are often difficult to achieve together, as improving one can often diminish the other.
Improving the traction properties of tire treads without sacrificing tread wear is thus highly desirable. Use of isobutylene-based elastomers in blends with hydrocarbon diene-elastomers often serves to increase tangent delta values at temperatures at or below about 0° C. (predicting potential improvements in tire wet and winter traction). However, lab abrasion resistance is often decreased, predicting poorer tread wear. Use of isobutylene-co-p-methylstyrene copolymers increases the compatibility of isobutylene-based elastomers with hydrocarbon elastomers. Yet, co-vulcanization is still not achieved to a sufficiently high degree and lab abrasion resistance is still not at levels of NR, SBR and the like. Thus compound abrasion resistance still needs to be further increased for isobutylene-based elastomer blends, while maintaining the potential traction benefits of the polymer.
It is unexpected that the incorporation of a multiolefin derived unit in a isobutylene/p-methylstyrene backbone would contribute to both improved traction and abrasion properties in elastomer compositions. Yet, the inventors here demonstrate, among other things, the practical use of certain isoolefinic terpolymers that incorporate multiolefins. More particularly, it has been discovered that these terpolymers are useful in blends with natural rubber and the like due to improved traction and abrasion performance, thus making these compositions useful in tire treads and sidewalls.
Other background references include U.S. Pat. Nos. 3,560,458 and 5,556,907 and EP 1 215 241 A.